The present invention relates to a software defined radio in which a software library is controlled by distributed control scheme.
As broadband communication is spread, the diversity of communication system is quickly increasing even in a radio communication field. Such a tendency increases the need for a seamless wireless communication service by which the most suitable wireless systems are selected according to conditions including a communication purpose and a communication environment to achieve free data transfer between the wireless systems. For example, in the telematics service, a review is directed to the use of cellular system and wireless LAN; for the purpose of connecting a vehicle with the Internet, the employment of ETC (electronic toll collection) system for automatic toll payment, the use of near field communication for communication within a vehicle, and further the employment of digital terrestrial broadcasting system for viewing or listening to a television or radio. With the frequent modification or function addition of an existing communication system, the need for a radio facilitating the later system modification, function addition or defect correction has been spread, in particular, in infrastructure equipment including a base station as its representative.
As one of techniques for satisfying such a demand, there is a software defined radio technique. A software defined radio based on the technique processes signals for radio communication with use of a processor having a high processing capability and a reconfigurable digital signal processing device. When a DSP or a CPU is employed as the processor, software having the contents of the processed signals described therein is stored in a storage device such as a memory. The processor performs its signal processing operation by reading the software therein from the storage device. Various signal processing operations can be realized by modifying the description of the software or by exchanging the software. When an FPGA (Field Programmable Gate Array) is used as the reconfigurable device, configuration data having placement/routing information for desired signal processing is stored in the storage device such as a memory. The reconfigurable device can realize the signal processing by reconfiguring the placement and routing on the basis of the configuration data stored in the storage device.
For the purpose of using the software defined radio for a plurality of communication systems, when such the programmable processor, reconfigurable device, etc. having a general versatility as mentioned above are prepared as its hardware, the software defined radio can be commonly used for the plurality of communication systems. With respect to its software, on the other hand, the number of pieces of software is required to correspond to a desired number of such communication systems to be realized. When it is desired to realize the radio in the form of exclusive hardware, complicated LSI design is required and an enormous amount of time is required for its realization. Since the software defined radio can use the hardware commonly, it is only required to design the software. However, in general, a considerable amount of time is required even for software design.
Most of the items of signal processing carried out in the radio are carried out commonly by the communication systems. For example, modulation/demodulation, spreading, encoding, scrambling, CRC, etc. are not operations unique to a specific communication system but signal processing operations required by most communication systems. For this reason, it is considered to form these signal processing operations into software libraries as units to be commonly used to the communication systems. The communication system can be realized by a combination of these unit libraries. Since the library is software, hardware for realizing the processing operation is required. When a processor is used, the library has a program for realizing each processing operation described therein. When a reconfigurable device is used, the library is configuration data having placement/routing information for realizing each processing. The processing can be implemented by reconfiguring the placement and routing of the reconfigurable device. The required communication system can be realized in the form of a combination of the signal processing libraries, thus eliminating the need for designing the software from its beginning.
In a conventional exclusive radio apparatus, signal processing blocks for realizing these library processing operations are centralizedly controlled. FIG. 1 schematically shows a centralized control system. In FIG. 1, signal processing blocks 102 to 105 perform unit processing operations of modulation/demodulation, spreading, encoding, etc. In the centralized control system, a timing controller 101 for collectively controlling the timing of the signal processing blocks 102 to 105 is necessary. In a software defined radio to which the control method is applied, each of the signal processing blocks 102 to 105 is formed as a reconfigurable device or the like. The signal processing blocks 102 to 105 are subjected to placement and routing on the basis of the configuration data having the library operation (such as modulation/demodulation, spreading or encoding) desired in the corresponding signal processing block described therein. In the centralized control system, consider now a case where it is desired to change a certain part of the library. When the change of the library is carried out, it is required to change not only the library but also the timing controller for controlling the library in question. In addition, it is inevitably required to also change the libraries belonging to the timing controller other than the corresponding library. As a result, it is necessary to rewrite the entire software and thus the benefit of the librarization cannot be taken.
In view of such a problem, a system for distributedly controlling libraries is considered. In this control system, the signal processing blocks having the signal processing libraries installed therein have a common interface. Data input/output are carried out synchronously with a clock signal together with control information indicate of a data type. Since timing information is transmitted as control information simultaneously with data, the need for provision of a timing centralized controller can be avoided and the signal processing blocks can perform their timing control independently of each other. So long as data input/output between the signal processing blocks are synchronized, it is unnecessary to synchronize the operations of function parts. Thus the independency of each signal processing block can be secured and the control of the libraries can be based on distributed control. An example of a system for distributed control of libraries is disclosed in “A study on Software Defined Radio (2)-Software Library-”, Manabu Kawabe, et al., IEICE Communications Society, 2004 General Conference Transactions, B-17-7, released on Sep. 23, 2004.